Chapter 2: The Research Enterprise in Psychology.

Chapter 2: The Research Enterprise in Psychology

The Scientific Approach:A Search for Laws

• Basic assumption: events are governed by some lawful order

• Goals:– Measurement and description– Understanding and prediction: psychologists form

hypotheses about how variables interact. • A hypothesis is a tentative statement about the

relationship between 2 or more variables. • Variables are the things that are observed or

controlled in a study.

The Scientific Approach:A Search for Laws

• Goals (cont.):– Application and control: information

gathered by scientists may be of some practical value in helping to solve problems

Figure 2.1 Theory construction

Figure 2.2 Flowchart of steps in a scientific investigation

The Scientific Method: Terminology• Operational definitions are used to clarify

precisely what is meant by each variable• Participants or subjects are the organisms

whose behavior is systematically observed in a study

• Data collection techniques allow for empirical observation and measurement

• Statistics are used to analyze data and decide whether hypotheses were supported

The Scientific Method: Terminology• Findings are shared through reports at

scientific meetings and in scientific journals – periodicals that publish technical and scholarly material– Advantages of the scientific method: clarity

of communication and relative intolerance of error

• Research methods: general strategies for conducting scientific studies

Table 2.1 Key Data Collection Techniques in Psychology

Experimental Research:Looking for Causes

• Experiment = manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed– Detection of cause-and-effect relationships

• Independent variable (IV) = variable manipulated or controlled

• Dependent variable (DV) = variable affected by manipulation – How does X affect Y? – X = Independent Variable, and Y =

Dependent Variable

Experimental and Control Groups:The Logic of the Scientific Method

• Experimental group: who receives a special treatment in regard to the independent variable

• Control group: who do not receive the special treatment– Manipulate independent variable for one

group only – Resulting differences in the two groups

must be due to the independent variable

Experimental and Control Groups:The Logic of the Scientific Method

• Extraneous and confounding variables– An extraneous variable is a variable, other than

the independent variable, that may influence the dependent variable.

– Confounding of variables occurs when participants in one group of subjects are inadvertently different in some way from participants in the other group, influencing outcome.

• Random assignment: Random assignment of subjects is used to control for confounding variables

Figure 2.5 The basic elements of an experiment

Experimental Designs: Variations

• Expose a single group to two different conditions– Reduces extraneous variables

• Manipulate more than one independent variable

- Allows for study of interactions between variables

• Use more than one dependent variable

- Obtains a more complete picture of effect of the independent variable

Figure 2.6 Manipulation of two independent variables in an experiment

Strengths and Weaknessesof Experimental Research

• Strengths: – conclusions about cause-and-effect can be drawn,

No other research method has this power.• Weaknesses:

– artificial nature of experiments; researchers must create fake settings so that they have control over the environment.

– ethical and practical issues: malnourish infants on purpose to see what the effects are on intelligence

– Others cannot be done because of practical issues…no way to assign families to live in urban vs. rural areas to determine the effects of city vs. country living.

Descriptive/Correlational Methods:Looking for Relationships

• Methods used when a researcher cannot manipulate the variables under study– Naturalistic observation– Case studies– Surveys

• Allow researchers to describe patterns of behavior and discover links or associations between variables but cannot imply causation

Figure 2.10 Comparison of major research methods

Descriptive/Correlational Methods:Looking for Relationships

• Advantages and Disadvantages:– Naturalistic Observation:

• ADV: less artificial• DIS: hard to stay unobtrusive; can’t show cause

and effect or why certain behaviors were observed

– Case Studies:• ADV: good for studying specific phenom.; can

provide real examples to support some theories• DIS: often leads to psy. Seeing what he/she

wants; clinical samples often unrepresentative

Descriptive/Correlational Methods:Looking for Relationships

• Advantages and Disadvantages (cont.):– Survey:

• ADV: easy to gather data on hard to observe behaviors; easy way to collect a large amount of data

• DIS: data often unreliable due to intentional deception, social des. Bias, response sets, memory lapse, and wishful thinking

Statistics and Research:Drawing Conclusions

• Statistics – using mathematics to organize, summarize, and interpret numerical data– Descriptive statistics: organizing and

summarizing data– Inferential statistics: interpreting data and

drawing conclusions

Descriptive Statistics:Measures of Central Tendency

• Measures of central tendency = typical or average score in a distribution

• Mean: arithmetic average of scores• Median: score falling in the exact center• Mode: most frequently occurring score

– Which most accurately depicts the typical?

Figure 2.11 Measures of central tendency

Descriptive Statistics:Variability

• Variability = how much scores vary from each other and from the mean– Standard deviation = numerical depiction

of variability• High variability in data set = high

standard deviation• Low variability in data set = low standard

deviation

Figure 2.12 Variability and the standard deviation

Descriptive Statistics: Correlation

• When two variables are related to each other, they are correlated.

• Correlation = numerical index of degree of relationship– Correlation expressed as a number

between 0 and 1– Can be positive or negative– Numbers closer to 1 (+ or -) indicate

stronger relationship

Figure 2.14 Interpreting correlation coefficients

Correlation:Prediction, Not Causation

• Higher correlation coefficients = increased ability to predict one variable based on the other– SAT/ACT scores moderately correlated

with first year college GPA • 2 variables may be highly correlated, but not

causally related– Foot size and vocabulary positively

correlated– Do larger feet cause larger vocabularies?– The third variable problem

Figure 2.15 Three possible causal relationships between correlated variables

Inferential Statistics:Interpreting Data and Drawing Conclusions

• Hypothesis testing: do observed findings support the hypotheses? – Are findings real or due to chance?

• Statistical significance = when the probability that the observed findings are due to chance is very low– Very low = less than 5 chances in 100/ .05

level

Evaluating Research:Methodological Pitfalls

• Sample: collection of subjects chosen for observation in a study

• Population: larger collection from which researchers want to generalize about

• Sampling bias: when a sample is not representative of the population

• Placebo effects: when a participant’s expectations lead them to experience some change even though they receive empty, fake, or ineffectual treatment

Evaluating Research:Methodological Pitfalls

• Distortions in self-report data:– Social desirability bias: a tendency to

give socially approved answers to questions about oneself

– Response set: a tendency to respond to questions in a particular way

• Experimenter bias: when a researcher’s expectations or preferences about the outcome of a study influence the results obtained – the double-blind solution

Figure 2.16 The relationship between the population and the sample

Ethics in Psychological Research:Do the Ends Justify the Means?

• The question of deception • The question of animal research

– Controversy among psychologists and the public

• Ethical standards for research: the American Psychological Association– Ensures both human and animal subjects

are treated with dignity

Figure 2.17 Ethics in research

Ethics in Psychological Research:Do the Ends Justify the Means?

• APA Guidelines:– 1. Participation must be voluntary and based on

informed consent and people must be able to withdraw

– 2. No exposure to harmful or dangerous procedures (psy. and phys)

– 3. Researchers must debrief ASAP– 4. Right to privacy must not be violated– 5. Harmful procedures on animals must be

justified in terms of knowledge gained– 6. Researchers must obtain permission from host

institutions and review committees prior to starting a study.